Aluminum alloy



Patented Feb. 13, 1940.

NI E STATES PATENT OFFICE I amass summon mo! No Drawing. Application May8, 1939, Serial No. 272,520

-3 mm. (cl. -149) This invention relates to an improvement in aluminumalloys. More particularly, it has in view alloys of aluminum which maybe used for most industrial requirements without heat treat- 6 ment andwhich has special machining qualities,

and also exhibits desirable physical characteristics in the way of hightensile strength, suitable hardness, and a high degree of elongation.The alloys combine with these qualities a number of 0 other advantagescharacteristics, such .as resistance to oxidation and corrosion. Thealloys are of extremely fine grain, and machining operations result in asurface of a highly finished appearance.

15 These alloys, as stated, have high tensile strength and elongationwithout heat treatment, and while other alloys, after heat treatmentinvolving additional expense, may show comparable tensile strength andelongation, the cost of manufacture is greater and they have thedisadvantage of losing the increased physical characteristics, such astensile strength or elongation upon being subjected to heatingoperations. The

alloys of the formula herein set forth when used without special heattreatment-may be freely welded or subjected to heating effects withoutlosing the characteristics stated. They at all times exhibit thequalities or high tensile strength and a high degree of elongation, andat the same time provide the most satisfactory material for precisionmachining operations.

The alloys are of very wide application industrially, and while in noway limited to use for fabrication of various structural parts for ma-85 chines and the like, they are particularly suited for such use,especially in equipment requiring precision of manufacturev andgoodappearance.

Heretofore there have been many alloys embodying various proportions ofaluminum, mag

nesium, copper and the like, and certain elements, such as titanium,have been used to improve the grain structure of the finished product.However, in many instances the alloys heretofore produced have involvedcomplicated steps in alloying of the various elements, or in thedevelopment of tensile strength of the alloys throinh heat treatment andthe like, and this expense and the incidental disadvantage 01' heattreatment are avoided in the present inventio The principal object ofthe invention is to provide alloys wherein the aluminum content ismaintained at a relatively high percentage, and wherein the otherelements of the alloy are acas curately proportioned to have combinedaction to increase the tensile strength of the finished product.

Another object of the invention is to provide alloys of aluminum havinga high degree of tensile strength without sacrificing other desirable Iphysical characteristics, such as high degree of elongation.

Another object of the invention is to provide aluminum alloys havinghigh tensile strength, and a high degree of elongation and physical 10characteristics without the necessity of heat treatment for suchproduct.

Another object of the invention is to provide an aluminum alloyresistant to corrosion, and at the same time having an unusual degree of1 tensile strength and elongation, and adapted for machine operations toa greater degree than other alloys having like physical characteristics.

Another object of the invention is to provide an alloy of aluminum foruse without heat treatl0 ment, but having a high degree of tensilestrength and elongation comparable to those of heattreated alloys, whichmay be freely'welded without losing such high degree of tensile strengthand elongation and other physical characteris- 25 ties as would be thecase with'alloys receiving the original heat-treating eiiects.

Other and further objects of the invention will appear in the ,courseofthe following description. a The preferred form of alloy includes withother elements added'to a high percentage of aluminum,

a small quantity of titanium, such element, however, being prei'erablyadded in the form of ferrotitanium instead as a titanium aluminum richalloy. Normally the addition of iron to an aluminum alloy is notfavored, but where such amount of iron is kept at a minimum and in closeassociation with titanium such addition of a fractional per cent of ironis of no disadvantage and it apparently has the effect of speeding upthe process of aging the alloy.

The preferred formula foran alloy of a high degree of tensile strengthand at the same time a a high limit of elongation comprises thefollowing: v

Specimens made in accordance with the above formula have shown a tensilestrength of from 30,220 to 31,000 pounds and' an elongation of from 7per cent to 8 per cent.

As stated the fractional percentage of iron present apparentlyaccelerates the aging process. The use of term-titanium provides a readymeans of introducing a satisfactory proportion of titanium and iron.However, the alloy may be made by adding titanium rich aluminum and atrace of iron may be present in the aluminum.

In the latter case amount iron may range from a trace to .40 per centand the following formula is to be used:

Aluminum 93.30 to 93.70 Titanium .15 150 .30 Copper 1.50 to 2.00 Tin1.50 to 1.75 Zinc .75 to 1.00 Magnesium .90 to 1.00 Chromium .20 to .25Iron trace to .40 Variations may be made slightly above and below theelements set forth in the several formulas, as has been indicated, thealuminum content being the residual amount, required. The

exact physical results to be attributed to any particular element is notfully understood. but it is believed that the interaction of theelements added to the aluminum upon each other is clearly indicated. Thetitanium and tin together produce an unusuallyflne grained dense producthaving great tensile strength,-'and at the .same time having exceptionalcapacity for free machining, and presenting a finished surface afterhaving been so machined. The combination of elements set forth producesan alloy in each instance of wide industrialapplication, which, inaddition to having high tensile strength and a high degree ofelongation, has fine appearance and capacity to resist oxidation andcorrosive eiiects. While in the instances above stated the alloys willbe round satisfactory tor most uses without subsequent heat-treatment,

it is not intended. to restrict the use of the invention to the extentthat certainspecialized 7 treatment will not be applied in the eventsome very unusual application of the alloys is to bemade,particularlyunder certain high temperature conditions, or wheresome extraordinary specifications have to be fulfilled. The widespread,and almost universal use of the alloys, without heat treatment, isprovided for by the special 10 formulas above set forth, which, asstated, have the advantage of low cost of production, and permanence ofphysical characteristics, when welding or like operations are carriedout.

Other modes of applying the principle of my invention'may be employedinstead of those explained, change being made as regards the means andsteps herein disclosed, provided the means stated by any of thefollowing claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. An alloy of aluminum consisting. of about 93.30 per cent of aluminum,.30 per cent of titaniuin, 2.00 per cent of copper, 1.75 per cent oftin, 1.00 per cent of zinc, 1.00 per cent of ma nesium, .25 per cent ofchromium, and .40 per cent of iron.

2. An alloy of aluminum consisting of about .15 to .30 per cent oftitanium, 1.50 to 2.00 per 80 cent of copper, 1.50 to 1.75 per cent ofzinc, .75 to 1.00 per cent of magnesium, .20 to .25 per cent ofchromium, from a trace to .40 per cent of iron, the balance beingaluminum.

3. An alloy of aluminum for use without heat 25 treatment consisting offerro-titanium having approximately equal parts of iron and titanium ofan amount ranging from .30 to .70 per cent, 1.50 to 2.00 per cent ofcopper, 1.50 to 1.75 per cent of tin, .75 to 1.00 per cent of zinc, .90to 1.00 40 per cent of magnesium, .20 to .25 per cent of chromium, thebalance being aluminum.

EDWARD A. so.

